Potable water is the most basic need in the desert. Approximately 75% of the human body is fluid. A loss of two quarts decreases efficiency by 25% and a loss of fluid equal to 15% of body weight is usually fatal. Approximately 8 litres of water per soldier per day is ideally needed in desert terrain. It is important to separate drinking and non-drinking water. Drinking any water from an untested source is dangerous. Diseases commonly found in a desert environment include plague, typhus, malaria, dysentery, cholera, and typhoid. Because of water shortages, sanitation and personal hygiene are often difficult in arid regions. If neglected, sanitation and hygiene problems may cripple entire units. Drinking impure water brings dysentery.
However, water is often scarce as it can take almost 40% of the Army's daily logistical load in the dessert, or nearly 25 litres of water per soldier per day, when medical treatment, meal rehydration and bathing are factored in. For example, pots, pans, utensils and other dishes are washed, rinsed and sanitized in the field with a three-sink food sanitation centre that consumes nearly 250 gallons of drinking water daily, which is either poured onto the ground, or stored in a tank or bladder for disposal. So, there is enough waste water to use as auxiliary fuel to reduce the use of batteries and yield a small amount of fresh hot water too.
If we bear in mind that about 20 gallons of fuel per soldier per day are also needed (this includes air support, electricity, climate, cooking, driving, etc.) to which we have to add the batteries both rechargeable and standard that a soldier needs, that does not leave very much room for anything other than ammunition, particularly in Afghanistan. Therefore, the real challenge that must be overcome is providing enough water and energy to our troops.
In today’s high-tech Army, where even the smallest patrol counts on a wide range of electronic systems — including radios, network terminals, night-vision goggles, radio jammers and shoulder-fired rockets — batteries are a critical resource. In many missions the batteries are heavier than the ammunition they are carrying. Some missions require as much as 100 pounds of equipment.
Some years ago, a soldier on average would consume three to four watts of battery power on a typical mission, but now he consumes around 20 watts. To provide his 20 watts, a soldier might carry as many as eight 2.2-pound BA-5590 lithium sodium dioxide batteries on a mission, in addition to smaller alkaline batteries, for a combined weight of around 20 pounds. As a result, battery weight and size have become important factors in mission planning. Existing military batteries can provide enough power for computer displays, radios, sensors, and electronics for a 12-hour mission, but longer missions will require other technologies to efficiently power operations lasting up to 72 hours.
The traditional methods for the war fighter to replace used battery cells is to either discard or turn in the old cell at a supply location and get restocked, expending valuable time.
A rechargeable battery pack saves costs in materials and saves the time expended going to and from the supply depot, but the soldier must have a readily available charging system in the field. On the other hand, disposable, non-rechargeable batteries can keep the war fighter in the field longer, with immediate replacements available, but it means carrying 65 batteries per man in average (8 kilograms) per three days of mission. A combination of the two (rechargeable and disposable) could be the answer. The soldier can recharge the battery pack as often as is practical in the field when a charger becomes available. At others times, disposable batteries maintained in the soldier’s uniform can be used. This keeps the war fighter mission-ready.
Stocking of rechargeable batteries requires significant maintenance, keeping track of the battery’s state of health, cycle count, and age. Due to high self-discharge, nickel-based batteries exhibit a 10-20% self-discharge per month. This compares with 5-10% for lithium and lead-based batteries. Self-discharge increases at higher temperatures. Monitoring of effective battery power is a significant aspect for military use, but it is rarely available with primary batteries. While such implementations add to the cost of each battery, they reduce the total life cycle cost of the entire battery inventory.
Our power pack generates energy from waste liquids such as urine, stagnant or used water, scavenging the available energy that can be derived from water combined with solar power. Our innovation is able to deliver, using up 1kg of magnesium in the process, power efficiently with varying demand (1.244kWh), water (¾ Litre) and heat (0.052 kWh) per kilogram of magnesium, using a device that we estimate will weigh approximately 5 kilograms empty. So, if we assume an energy budget of 400 Wh per day per soldier, on a 10-day mission the device can deliver all the power needed as well as heated fresh 1½ Litres of water for a weight of 8 kilograms (5 kg for the device plus 3 magnesium cartridges).
This device (40x30x15 cm. & 5kg.) is for individual use on operations where no facilities are available, rather than the better-equipped company-sized and up facilities. It can be used to directly power personal devices or to re-chare batteries. Larger facilities have diesel-powered generators which are more cost-effective, though not as eco-friendly as our power source. Although, this innovation could be used anyway to take advantage of the used water available.
Moreover, if a combat team has to be re-supplied, our power packs enable a substantial reduction in the number of batteries to be supplied, as well as a modest reduction in the amount of water; where the fresh water supplied by the power pack is also hot so it can be used to re-hydrate food or make a hot drink in the field.
Stocking of rechargeable batteries requires significant maintenance, keeping track of the battery’s state of health, cycle count, and age. Due to high self-discharge, nickel-based batteries exhibit a 10-20% self-discharge per month. This compares with 5-10% for lithium and lead-based batteries. Self-discharge increases at higher temperatures. “Smart” monitoring of effective battery power is a significant aspect for military use, but it is rarely available with primary batteries. While such implementations add to the cost of each battery, they reduce the total life cycle cost of the entire battery inventory.
In terms of logistics, this power pack is a vastly superior option to using lithium-ion or rechargeable batteries only. Power packs would be taken into theatre and in order to keep functioning, they would need magnesium cartridges, which would in remain in-theatre since they do not pose a fire or environmental risk. Magnesium hydroxide can simply be buried or thrown away in any field.
Since the cartridges do not decay they do not have to be checked or recharged like batteries. Most importantly, the power packs or cartridges do not have to come back along the supply lines.
Typically, a small unit could take a power pack and recharge other batteries or run some electrical equipment directly from the power pack. Versions could be implemented for individual use or for small special forces use. The weight advantage is more than 6:1 compared to lithium-ion batteries and as an operation progresses, the weight would reduce unlike the case of batteries being used, which have to be brought back along the supply lines. This approach would reduce the weight being carried by soldiers and the need for re-supply while on longer-lasting operations.
The power pack would only need to be rinsed regularly to remove magnesium solids and its main water-rich liquid vessel, before being reloaded with a new cartridge and used.
If and when power packs are damaged or have malfunctioned for some reason, only the central instrumentation core would have to be brought back, which weighs 3 kilograms and is only about a quarter of the power pack dimensions, the rest being the three vessels: water-rich fluid, fresh water and the magnesium by-products chamber that can be left behind.
Energy from waste liquids such as urine, stagnant water or used water, scavenging the available energy that can be derived from water combined with solar power. Ours is a new design with dual functionality both as a power-generating device, replacing expensive and heavy batteries, as a fresh water purifying means AND heat source for the individual soldier in-theatre, away from normal facilities.
CURRENT RELATED PROJECTS
We currently have a number of related projects in progress that make our supplying this solution more viable than alternative sources, namely:
- A fuel cell based on a magnesium-air process using sea water, currently being built for a marine long-endurance uav for the Mexican Navy, which has a 7,000 miles coastline to patrol.
- A magnesium fuel cell aided by water recovery from the atmosphere by condensation, for a HALE uav currently being developed by the Ecuadorian Air Force.
- The onboard computer including avionics for a power-line monitoring blimp currently being developed for the Mexican Electricity Board (CFE) in collaboration with a Mexican partner CIDEP SA.
- The onboard computer including avionics for a short-range tactical fixed-wing UAV being developed by Aeroriel SA.
- A LINUX-based ground control station, including autopilot, geographical information system and route planning, for a blimp and a tactical fixed-wing UAV.